“…Four studies compared PsA patients to patients with psoriasis without arthritis [29,33,39,40]. In all, seven studies compared PsA patients to other inflammatory rheumatic diseases: four studies to rheumatoid arthritis (RA) [23,30,34,41], two to ankylosing spondylitis (AS) [22,38], and one study to early spondyloarthritis [32]. Four studies compared PsA patients to normal controls [20,31,35,36].…”